Air blast circuit breaker



H. MILLIKEN AIR BLAST CIRCUIT BREAKER Oct. 17, 1950 3 Sheets-Sheet l Filed Jan. 24, 1946 RMILLI KEN l Oct. 17, 1950 H. MILLlKl-:N

un Bus'r ciRcuI'r mm 3 Sheets-Sheet 2 Filed Jan. 24, 1946 FIG .10

mvEN-ron H MxLuKEN TTORNEI Oct. 17, 1950 H. MILLIKEN 2,526,337

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ATTORNEYS' Patented Oei. 17, 1950 UNITED sTATEs PATENT OFFICE AIB BLAST CIRCUIT BREAKEB Humphreys Milliken, Mount Royal, Quebec, Canada Application January 24, 1946, Serial No. 043,.

(CL 2l 148) 13 Claims. l

Ihis invention relates to air blast circuit breakers used to interrupt short circuit currents in power systems of larse capacity.

One object of this invention is to provide an assembly of interrupting elements with a maximum interrupting capacity in a given space or a given required interrupting capacity arranged so as to occupy a minimum space and use a minimum amount of air.

Another object is to provide a circuit breaker designed to interrupt a short-circuit current with a minimum duration of arc.

Other objects, advantages and characteristic features of the invention will become apparent from the following detailed description of the drawings, in which- Pig. l is a view, partly in elevation and partly in vertical section, oi the live parts of a circuit breaker embOdying my invention.

Pig. 2 is a part sectional view on section line 2 2 of Pig. 1.

Pig. 3 is a sectional view taken substantially along section line 3 3 of Pis. l. In this view the path of the arc is indicated by a string of small dots.

Fig. 4 is bottom plan view of the assembly shown in Fig. 3 with certain elements omitted permit of a diagrammatic dotted line showing the path of the arc. Pig. 5 is a cross sectional view of certain elements appearing in Fig. 3, the plane of the section being substantially along section line 5 5 of Fig. 3. In this view certain elements that would otherwise appear in a section taken along line 5 5 have been omitted for the sake o! clearness.

Pig. 6 is a view similar to Fig. 3 but showing a slight modiiication.

Pig. I'I is a side view of a portion of the assembly shown in Fig. 6.

Fig. B is a cross-sectional view on section line l-I of Fig. 6.

Fig. `9 is a bottom plan view of a portion of the assembly shown in Pig. 6.

Fig. 10 is an enlarged sectional view on line Il ll of Pis. 6.

Referring more particularly to Pigs. l and 2. l designates an interrupter housing cylinder mounted on casting l cemented to the upper portion of porcelain tube 1. Casting 6 also serves to house and support interrupter contact l to which current is conducted through said casting from station connections 9: it being noted that contact I is secured to casting 6 by rivets orother metal fastening means Il.

.Sil

Tube 1 supports a metal blade-moimting casting Il provided with extension Ila aordlng a second station connection I2. 'I'he lower end of a curved interrupter blade I3 is pivoted to a second extension Il of casting II as indicated at Il. Blade Il includes a horn portion I5 curved on a radius with center at hinge i5. Hom I6 travels in a. vertical plane about hinge i! and is movable inwardly and outwardly through a side opening I1 of housing cylinder 5 to make and break contact with interrupter contact l.

An arc chute assembly A, which constitutes the principal feature of the invention and is hereinafter more speciiically described, is arranged in housing cylinder 5 immediately above opening I1.

The opening and closing movement of blade i3 may be eected by any suitable mechanism such, for example, as the blast operated mechanism disclosed in my United States Patent No. 2,396,742, granted March 19, 1946. When the horn i6 separates from contact 6 during the opening movement of blade I2 the arc is transferred from contact l to an arcing contact I8 carried by a copper support Il which is fastened to casting 6 as indicated at 2l. A libre block 2| is fastened to support I9 to minimize leakage of air through opening 22 of housing cylinder 5.

Cylinder 5 is lined with insulating material 23 shaped to provide, in conjunction with :the bore of porcelain tube 1, an air blast passage of varying shape and cross-section. 'I'he bore 1a of tube 1 is circular in cross-section and constitutes part of the entrance end or inlet section of said air passage.

In order to facilitate understanding of the configuration of that part of the air blast passage which is deiined by the insulation lining 2l, the front, rear, right and left sides of the interrupter have been indicated by legends and the direction ot travel of the arc-extinguishing air blast has been indicated by arrow 25.

The circular section of the air blast passage aii'orded by the bore 'la of tube 1 merges into a section 26 of approximately rectangular shape, the right and left sides 21 and 28 of which converge to a relatively narrow throat or constricted section 29. The front wall I0 of section 26 extends straight up while the rear wall Il curves vupward and backward as shown in Fig. l. The horizontal cross Section of the throat or constricted portion 29 has a length (as measvtired from back to front) equal to about six amasar times its width (as measured from left to right) Abovethe constricted throat 29, the air blast passage widens to provide an expanding section 32 having right and left sides ilaring outward at an angle between 45 and 60. The front and back walls of expanding section 32 extend straight up- The section 33 of the air blast passage located above the ilaring side walls-of section 32 has a constant horizontal cross section which is approximately square, thus utilizing the maximum available cross section within circular cylinder 5.

Section 34 of the air blast passage located above insulating material 23 is a circular section utilizing the i'ull cross sectional area of cylinder 5 to minimize air resistance and back pressure and to obtain maximum air velocity in the throat section 29 and maximum interrupting capacity. A cooling grid, not shown, may be arranged in section 3l in spaced relation to arc chute assembly A to provide an intervening empty space constituting a mixing chamber'in which the hottest and coolest streams of air and gas mingle, assuming an average temperature, and expand to iill the circular section 34 before entering the cooling grid.

'I'he arc chute assembly A includes a partition unit shaped to iit snugly into the expanding section 32 and the approximately square section 33 of the air blast passage. I'his partition unit comprises main and intermediate partitions composed of vulcanized hard horn libre having the property of vaporizing at its surface when touched by the are. With the air blast blowing away the vaporized iibre as fast as it is formed, the libre surface retains its dielectric strength.

In the present instance I have shown iive main partitions 36a, 36h, 39e, 36d and 36e arranged in spaced relation in parallel planes which are perpendicular to the plane of motion of horn I6 and are also perpendicular to a geometric straight line drawn between the ends of the arc on arcing contact I 3 and on the upper edge of horn I9.

The bottom or Windward edge 39 of each of the main partitions 36a, 39h, 36e, 38d and 36e extends across the constricted or throat section 29 oi' the air blast passage and is upwardly and leewardly inclined at an angle suflicient to cause the impinging arc to shift quickly to the uppermost leeward point on said edge. The bottom edges 38' of adjacent main partitions are inclined upwardly in opposite directions. i. e., the lower edges of the main partitions 39a, 36e and 36e are inclined upwardly to the left while the lower edges of the remaining main partitions 36h and 36d are inclined upwardly to the right. By this arrangement the arc is deiiected` and held on the lower edges of said main partitions at relatively staggered points alternating from the right to the left side of the constricted throat 29 of the air passage, where the velocity of the air blast is at its maximum with maximum interrupting capacity.

The aforesaid lower Windward edge 39' oi' each of said main partitions may have a bent profile as shown in Figs. 2 and 3; may be straight as shown in Fig. 6; or may have a continuous curve so long as the highest point is located well to the right or left (alternately) of the vertical plane passing through the center line (hereinafter referred to as the geometric central plane) of the throat portion 29 from front to back of the interrupter structure which is the plane of the Paper in Fig. 1. Furthermore, the Windward edges 36 o! said main partitions may be sharp as lndite@ 4 in Figs. 1, 'l and 9, or rounded, as indicated in Fig. 4.

The main partitions 36a, etc. are interconnected by intermediate partitions 33 consisting of fibre bars. The center lines oi these bars are in the central geometric plane oi the arc chute portion of the air blast passage which consists of throat section 29 and the sections 32 and 33 lying at the leeward side of the throat section. 'I'he lower or Windward edge oi each bar as a pointed shape 38a, preferably with a sharp edge, against which the arc is blown and held until brokenby the air blast. As shown in Figs. 3 and 6, the aforesaid main and intermediate partitions of the partition unit, under the action of the air blast, serve to force the arc into a pair of loops L (hereinafter termed sub-loops) between adjacent main partitions 36a etc., the greater width of the loops being approximately in a plane parallel to said main partitions. If the intermediate partitions 38 were omitted each pair of sub-loops L would obviously become one single loop which would constitute a workable arc looping arrangement but would be much less eiective than thearrangement shown.

As clearly shown in Figs. 1 and 10, the expanding portion oi the arc chute is divided, by the main partitions 36a, etc., into a plurality of air passages, one passage being nearest the front of the interrupter, another passage being nearest the rear of the interrupter and the remaining passages being in between the front and rear passages. On referring to Fig. 2 it will be noted lthat each intermediate partition 38 divides one of the iirst mentioned passages into right and lei't passages. In this connection it will be noted that each intermediate partition 33 is in contact with two adjacent main partitions throughout the length of the intermediate partition in the direction of the air now indicated by the arrow 25. The two passages into which the space between adjacent main partitions is divided by the interposed intermediate partition may be referred to as sub-passages. To denne the position of the intermediate partitions between the subpassages each of the latter may be said to be bounded by two of the main partitions at opposite sides of the sub-passages.

It may be pointed out here that, even in the absence of the intermediate partitions 33, the arc looping arrangement obtained in accordance with my invention diiers from prior art procedure involving the use of so-called arc splitter" barriers. In certain prior art interrupters the splitters have notches at the center of their lower edges in all of the "splitters" With such an arrangement there can be no sizeable loops. In such prior art interrupters the splitter barriers are spaced very close together, te" or less, which is necessary in order to obtain sumcient aggregate interrupting capacity in a reasonable space. With such close spacing and with the notches all in line, the arc must remain substantially in the center plane and each loop, if formed, would be less than V2" wide. In order to have any substantial interrupting eiIect a loop must have substantial arc resistance and IR drop or voltage from end to end of the loop; but any substantial voltage across the air gap of less than 1/2" would ash across and y eliminate the loop; hence there can be no eil'ective looping in such interi-unters; their only effective interrupting action is confined to the edges. y

With the construction shown in Figs. 1 to 10 assess? the intermediate Milon. Il

diagomlly opposite corners o! a rectangle h '96". the dillnnal being slightly more than one inch (see Figa. 4. 9 and i0). Furthermore. thisoneinchoiairinsulationhas ahigher dielectrlcitrengthperinchthanthecorresponding in the interrupters of prior art, because one space is more eilectively scavenged the air blast, due to the fact that the arc are blown away in widely divergins the two ends o! the loop. whereas, the prior art, the blowing away is in the same direction from the two main partitions where the are b held. two parallel streams of incandescent gases less than 95" apart.

the wlndward edges of the main partitions 36a etc.. show the direction in which each such windward edge is inclined and in which the are is thereby shifted by the air stream. The letter.; a, b, c and d indicate, respectively, the most leeward arc holding points on the windward edges of the partitions lia, IIb. c and ltd. Thus, the distance from point a to point b is the diagonal of the rectangular space the corners of which are indicated by letters a, t, b, s. In actual arc chutes built and tested the distance a to t is "/s" andato: %"whichmakesthediagonalatob slightly lower than 1".

Referring to intermediate partitions Il in greater detail. Pls. 3 shows one form of construction, this figure being a section on line 3 3 of l'lg. l. The cross-section shape of the pointed end of partition Il appearing in Fig. 3 is also shown in Fig. 5.

Starting at arcing contact Il (Fig. 3) the arc is driven by the air blast into the right side, the other end of the arc being held by the horn Il of blade I3. The arc is driven against the lower edge 3l' of main partition e and to the highest (most leeward) point e on said edge whence it can go no higher. 'I'hat portion of the arc which is held between the highest point on the edge 36 of main partition )le and arcing tip Il is nrst blown upward by the air blast into a single loop which, as indicated at l, strikes at its midpoint agaimt the sharp edge of a partition Il from which it cannot escape and is held there, each hal! of the single loop being then blown further upward into a pair of loops as shown. As the arc h blown around the lower corner of bar 3l it is blown into two channels )la cut in diagonally oppite corners oi' said partition 3l. This increases the distance (Figs. 4 and 10) between the ends of the half loops, thereby increasing the safety factor against short circuit across this space, which would eliminate the half loops. The het that the are actually follows such path has been proven by many tests, the path of the arc being shown by a light colored clean streak on the of the arc. Referring to Pigs. 6 and 8 lt rwill be noted that the arc, which is a series of dots. is blown info chanthat wall IIb stands between chanlla and the other end o! the sub-loop of the thus acts as a barrier between the two ends of the are sub-loop and increases the insulation between them.

I claim:

for drawing an are across said throat in the general direction o! its major dimension, a plurality of insulating partitions in said expanding section said partitions lying in geometric planes the extension of which would intersect the major dimension of said constricted section, the windward edges of said partitions being adjacent to the leeward portion of said constricted section and being inclined so that one part of each edge is further leeward than the remainder thereof, the most leeward point of each edge being on the side of said constricted section opposite to the most leeward point oi.' the next adjacent edge and the said most leeward points being substantially at the constricted section, the form and arrangement of the said Windward edges of the partitions being such that the most leeward points of said edges are unshielded and being also such as to prevent reduction oi the cross section of the arc until after the arc has reached said most leeward points.

2. An air blast circuit breaker including an air blast passage to which an arc extinguishing blast of air is delivered, said passage including a constricted throat portion of oblong cross section followed by an expanding section in which the cross section of the air stream is increased in the direction parallel to the minor dimension of the oblong cross section of said throat portion, means for drawing an arc across said throat in the general direction of its major dimension, a plurality of insulating partitions in said expanding section lying in geometric planes the extension of which would intersect the major dimension of said throat portion, the Windward edges of said partitions being adjacent the leeward portion of said throat portion and being inclined so that one end of each edge is further leeward than any other parts thereof, the direction of inclination of said edges being such that the most leeward points on the Windward edges of alternating partitions lie on one side ci said throat while the most leeward points on the edges of the remaining partitions lie on the opposite sides of said throat and the said most leeward points being substantially at the restricted section, the form and arrangement of thesaid Windward edges of the partitions being such that the most leeward points of said edges are unshielded and being also such as to prevent reduction of the cross section of the arc until after the arc has reached said most leeward points.

3. An air blast circuit breaker as set forth in claim 1, including intermediate partitions of insulating-wmaterial between said first mentioned partitions,` each intermediate partition being in contact with-two adjacent first mentioned partitions throughout the length of said intermediate partition in the direction of the air flow.

4. An air blast circuit breaker as set forth in claim 1, including intermediate partitions alternating with said nrst mentioned partitions, the

center-lines of said intermediate partitions in the directionof the air stream lying in a geometric plane approximately perpendicular to said first mentioned partitions.

5. An air blast circuit breaker as set forth in claim l, including intermediate partitions of insulating material between said rst mentioned partitions, each intermediate partition being in contact with two adjacent first mentioned partitions throughout the length of said intermediate partition, each of said intermediate partitions having its Windward end portion tapered to an edge, said tapered portion having channels extendingv along diametrically opposite corners thereof.

6. An air blast circuit breaker as set forth in claim 1, in which theuwindward edges of said partitions are sharp.

7. An air blast circuit breaker according to claim 1, including intermediate partitions of insulating material between said first named partitions, each of said intermediate partitions being in contact with two adjacent first named partitions throughout the length of said intermediate partition in the direction of the air flow and having the Windward end thereof shaped to a sharp edge.

8. An'air blast circuit breaker as set forth in claim 1, in which a portion of the air passage locatedleeward of said expanding section has a cross section which is approximately square in Qlexlall dimensions and in which said air passage includes another portion of circular cross section located beyond the square portion, the diameter of said circular portionbeing equal to or slightly U.greater than the diagonal across the square portion, said circuit breaker being further characterized in that the leeward end of said partitions terminate at the beginning of said circular portion which constitutes a'gas mixing chamber.

9. In an air blast circuit breaker, an arc chute through which a blast of air is discharged, means for drawing an arc across a constricted section of the arc chute through which the air passes, said constricted section being relatively short in the direction of the ow of air therethrough; being relatively wide in the direction of the arc as initially drawn thereacross; and being relatively. narrow in the direction perpendicular to the initial directionof the arc, an expanding section of the arc chute located on the leeward sideof the constricted section, spaced insulating partitions in said expanding section having their Windward edges extending across the outlet of the constricted section in a direction perpendicular to the initial direction of the arc, each of said Windward edges being inclined so that the edge is farther leeward near one side of said con- Ystricted section than at any other point on said edge, the Windward edges of adjacent partitions being inclined in opposite directions, the form and arrangement of the said windward edges of the partitions being such that the most leeward points of said edges are unshielded and being also such as to prevent reduction of the cross section of the arc until after the arc has reached said most leeward points and the said most leeward points being substantially at the constricted section.

10. An air blast circuit breaker as set forth in claim 9, in which each air passage separatingv two of the rst named partitions is divided into' two sub-passages by an intermediate partition joining said first named partitions so that each ub-passage is bounded by said rst named parti- 1ons. i

11. In an airblast circuit breaker, an arc chute through which a blast of air is discharged, means for drawing an arc across a constricted section of the arc chute through which the air passes, said constricted lsection being relatively short in the direction of the flow of air therethrough; being relatively wide in the direction of the arc as initially drawn thereacross; and being relatively narrow in the direction perpendicular to the initial direction of the arc. an expanding section of the arc chute located on the leeward side of the constricted section, spaced insulating partitions in said expanding section having their Windward edges extending across the outlet of the constricted section in a direction perpendicular to the initial direction of the arc, each of said Windward edges being inclined in alternate directions so that the arc is blown across said edge and is held thereon at the most leeward point of said edge, said holding points on adjacent partitions being on opposite sides of the geometric central plane through the arc chute, the arc being blown between holding points into loops diverging at wide angles from said geometric central plane, the form and arrangement of the said Windward edges of the partitions being such that the most leeward points of said edges are unshielded and being also such as to prevent reduction of the cross section of the arc until after the arc has reached said most leeward points and the said most leeward points being substantially at the constricted section.

12. An air blast circuit breaker as set forth in claim 11, including intermediate partitions positioned substantially in said geometric central plane, each of said intermediate partitions having its Windward edges positioned to hold one point of the arc near the outlet of said constricted section.

13. An air blast circuit breaker as set forth in claim 11, including intermediate parallel partitions positioned substantially in said geometric central plane, each of said intermediate partitions having its Windward edges positioned to hold one point of the arc near the outlet of said constricted section.

HUMPHREYS MILLIKEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

